Functional integrity of freshwater forested wetlands, hydrologic alteration, and climate change

Abstract

Climate change will challenge managers to balance the freshwater needs of humans and wetlands. The Intergovernmental Panel on Climate Change predicts that most regions of the world will be exposed to higher temperatures, CO2, and more erratic precipitation, with some regions likely to have alternating episodes of intense flooding and mega‐drought. Coastal areas will be exposed to more frequent saltwater inundation as sea levels rise. Local land managers desperately need intra‐regional climate information for site‐specific planning, management, and restoration activities. Managers will be challenged to deliver freshwater to floodplains during climate change‐induced drought, particularly within hydrologically altered and developed landscapes. Assessment of forest health, both by field and remote sensing techniques, will be essential to signal the need for hydrologic remediation. Studies of the utility of the release of freshwater to remediate stressed forested floodplains along the Murray and Mississippi Rivers suggest that brief episodes of freshwater remediation for trees can have positive health benefits for these forests. The challenges of climate change in forests of the developing world will be considered using the Tonle Sap of Cambodia as an example. With little ecological knowledge of the impacts, managing climate change will add to environmental problems already faced in the developing world with new river engineering projects. These emerging approaches to remediate stressed trees will be of utmost importance for managing worldwide floodplain forests with predicted climate changes.

Wetlands In a Changing Climate: Science, Policy and Management

“…At the same time, salinity intrusion poses specific threats to coastal freshwater wetlands because many species in these ecosystems are intolerant of salinity (Keddy 2010). Also, these species often have lower levels of production if salinity levels become too high (Middleton 1999;Sutter et al 2014;Middleton and Souter 2016). A recent review synthesizes the state of our knowledge on how salinization associated with climate change will impact these wetlands (Herbert et al 2015).…”

“…As demands for river resources increase, such problems are expected to worsen (Baron et al 2002). Flowing water is compromised by river re-engineering practices, even though moving water generally improves oxygenation and plant health (Middleton 1999). Also, upriver freshwater extraction in tidal freshwater wetlands coupled with sea level rise can cause the salinification of surface and ground water, with accompanying stress and even the collapse of tidal vegetation in the freshwater reaches of estuaries (Perry and Atkinson 2009;Middleton and Souter 2016).…”

Performance measures for a Mississippi River reintroduction into the forested wetlands of Maurepas Swamp

“…While surrogates of river reintroductions related to sediment releases from dams, spillways, or navigation channels that inadvertently convey sediments, nutrients, or freshwater are available in the literature (Hughes, 1997;Day and others, 2012;Middleton and Souter, 2016), the performance measures described herein were developed on the basis of what is known about healthy coastal swamp forests rather than on past restoration successes. It is expected that the Mississippi River reintroduction into Maurepas Swamp will increase the health of the Maurepas Swamp ecosystem by delivering fine sediment and nutrient subsidies and simultaneously flushing stagnant water and toxic metabolites from the system to keep salinity intrusion within established limits.…”

Palustrine forested wetland vegetation communities change across an elevation gradient, Washington State, USA

“…Addressing this gap in understanding where wetland plants occur relative to elevation, and how elevation corresponds to structure, may improve regional forested wetland conservation and restoration actions as forested wetland vegetation is naturally distributed across hydrologic gradients (Brinson, 1993;Keogh, Keddy & Fraser, 1999) and can be significantly altered by hydrologic modification (Middleton & Souter, 2016). For example, wetland restoration efforts intended to mitigate forested wetland loss often plant tree species at appropriate elevations relative to flooding so that plants successfully survive and grow and that restored wetlands' vegetation composition eventually resembles the composition of functional forested wetlands (Bledsoe & Shear, 2000).…”